Soil organic matter (SOM) plays a central role in nutrient (N, P, S, K) availability, soil stability and the flux of trace greenhouse gases between land surface and the atmosphere. It represents a major pool of carbon within the biosphere, estimated at about 1400-1500 x 1015 g globally, roughly two to three times that in atmospheric CO2 and acts as both a source and a sink for carbon and nutrients. To facilitate scientific progress in predicting the effects on SOM of changes in land-use, agricultural practice and climate, the need for a network of SOM modelers and long-term data holders was recognized. To fulfill this scientific need, the global Soil Organic Matter Network (SOMNET) was established during 1995 under one-year's funding as a Special Topic of NERC's TIGER program.